Wireless telephony and telegraphy.



A. W/SHARMAN. I WIRELESS TELEPHONY AND TELEGRAPHY.

APPLICATION FILED JULY 16, 1909. 942,044, Patented Nov. 30, 1909.

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ALEXANDER W. SHARMAN, 0F CLAPI-IAM, LONDON, ENGLAND.

WIBELES$ TELEPHONY AND TELEGRAPHY.

To all whom it may concern:

Be it known that I, ALEXANDER VVILLIAM SHARMAN, electrical engineer, a subject of the King of Great Britain, and residing at 179 Clapham'road, Glapham, London, England, have invented certain new and useful Improvements in and Relating to "Wireless Telephony and Telegraphy, of which the following is a specification.

This invention relates to an improved method and means for effecting telephonic or telegraphic communication between two or more stations without the employment of wires or artificial electrical conductors connecting such stations.

In carrying out my invention I make use of the well known fact that if an electric current be caused to pass between two separate earth or water contact plates the efiective path of the current is not confined to the right line joining such plates but is diffused or spread out over an extensive area; and that a small percentage of such current can be collected and utilized in a distant local circuit comprising a conductor joining two separated ground contacts and a sensitive current detector such as a telephonic re ceiver of suitable resistance.

The object of the present invention is to increase or extend the area over which these stray ground currents may be collected or detected and to this end the invention consists mainly in a novel method by which I110- mentary intense current impulses are produced from a low tension current source and in a form more suitable than has hitherto been available for this purpose. In connection with this method I prefer to employ a plurality of earth contacts each having a minimum of conducting surface, and joined in pairs and to use a self induction coil of a special form. I find both these features produce better results than do the earth contacts and inductance coils heretofore used.

I am well aware that the production of high tension current impulses from a low tension current source has already been attempted notably by means of transmitting apparatus consisting of an electric circuit,

provided with a battery or other convenient source of electrical energy, a self inductance coil, a telegraph key, an interrupter and an earth shunt around the break so arranged that when the circuit is broken the battery current and the extra current (due to self inductance) will be led to earth, whereas, at

Specification of Letters Patent.

Application filed July 16, 1909.

Patented Nov. 30, 1909.

Serial No. 507,972.

each make the battery circuit is completed both through the interrupter and the earth. I am also aware that it has been proposed to transmit speech by means of high tension current impulses to the earth by arranging in series a battery, a microphone and a selfinductance coil and placing an earth shunt around the microphone.

In carrying out my method in telegraphy, however, I do not employ an earth shunt in parallel with the break or microphone but I arrange the circuit in such a way that the high tension current waves or impulses when discharged from the self induction coil are not associated or combined with the low tension currents, derived from the battery. That is to say, the battery circuit to the earth is broken, or the current of the battery is reduced to a negligible quantity (owing to the high resistance of the microphone) at the moment of every high tension discharge. By arranging the low tension circuit and the self induction coil in this manner, I find that momentary intense currents are discharged from the coil which can be detected at a much greater distance than those produced by methods hitherto known.

In the accompanying drawings: Figure 1 illustrates diagrammatically a sending apparatus for carrying my improved method into effect; Fig. 1 illustrates my improved form of earth contacts; Figs. 2 and 3 are cross sectional views of forms of cores for the inductance coil which I prefer to employ.

The apparatus consists of a main electrical circuit which includes a source of low tension electrical energy such as a battery I) of primary or seconclar cells or a small dynamo. It also incluc es the winding of an impulse or self inductance coil, a current controlling device or electro-variable element (Z such as a microphone; an interrupter g; and a signal switch key 0. The current controlling device cl is for telephony and the controlling device 9 is for telegraphy as will be hereinafter explained.

The inductance or impulse coil is provided with a core or former 0, containing iron which should be in a finely divided or laminated state wound with insulated wire of conducting material. The dimensions of the impulse coil are determined by the resistance between the two earth plates employed and the selector switch marked f is set accordingly. It has been found preferable to concentrate the iron on the portion of the core nearest to the conducting winding, a suitable construction being a rod or tube of vulcanitc or other insulating ma terial (see Figs. 2 and 3) with iron distributed around it and the conductor av wound upon the whole.

A suitable construction is as follows: The diameter of the hollow iron core may be made one and a quarter inches, and the length of the same maybe twelve inches. The central portion of the core may be wound with ten layers of number fourteen standard wire gage double silk covered copper wire, the length of the wound portion of the core being about six inches. The ends of each layer of the winding are preferably connected to a separate contact stud of the inductance selecting switch f, as shown in Fig. 1. Either of the current controllers (Z or 5 above mentioned, and used respectively for telephony and telegraphy may be brought into circuit at will by the two-way switch 2', as will be readily understood. For telephony, the microphonic contact (Z is preferably of the granular type, and of a high resistance while the switch 2' is used in the position shown in full lines. Carborundum forms a suitable material for the granules either alone or mixed with carbon or metallic shot or filings, in suitable proportions. hen such microphonic contact is used practically all the battery current will pass through the self inductance coil (4, owing to its low resistance as compared with the high resistance of the earth circuit through which only an infinitely small proportion of the battery current will pass.

Then the apparatus is used for telegraphy the switch 2' is put over to the dotted line position and the current controlling device 9 comes into use. This device 9 may take the form of an intermittent contact breaker such as is in common use in connection with induction coils ;its contacts being shunted by a condenser h, to reduce the sparking and render the break as sudden as possible. The signal switch key 0 is similar in general construction to a single current Morse key used in line telegraphy and is provided with electrical contacts so arranged that in its normal position the receiving device, usually a telephone 7', is connected directly to the two receiving terminals of the apparatus marked 76 and Z and called impulse terminals. When the key 0 is depressed for the purpose of transmitting a signal the receiving telephone j is automatically disconnected, as will be understood. And when the key 0 is so depressed if the switch 2' is in its full line position, the terminal Z will be connected to the microphone d through said key, the coil a and switch f; while the terminal 7: will be connected to said microphone by the conducting wires, as shown. On the other hand,

if the switch i is in its dotted line position, the terminal Z will be connected to the controller 9 through said key 0, the coil a, and switch 7; while the terminal will be connected to the controller 9 by the wires shown. As the said microphone (Z and controller g are each connected to the battery I), it is evident that said terminals will also be connected to said battery whenever telephony or telegraphy is being employed. To each of the said impulse terminals Z and 7c are connected the radiating or distributing earth contact wires, such as shown in Fig. l. The terminals of the impulse coil are thus respectively connected to two or more ground plates or earth contact rods of small area, and preferably arranged in groups, as shown in Fig. l, the distance between such groups being as great as the space available permits. A number of independent rods or plates m, separated by a distance of not less than one meter and joined in pairs and at substantially right angles to each other, are found to give a better connection than a single plate of the same total area, for they are thus enabled to pick up the stray currents from all directions. At each station similar conduction or radiating systems serve the double purpose of transmitting and also of receiving the electrical energy. The system is characterized by the fact that the momentary intense currents required in the earth circuits are derived from the energy conserved in the circuits by the great electrical inertia of the impulse coil, a diminution of the battery current resulting in an increased current in the said circuit. And it will be observed that by distributing the earth contacts entirely around a circle of 860", the stray currents will be picked up no matter from what direction they may come.

Perfectly satisfactory signals have been obtained with the above described apparatus over a distance of half a mile with a primary energy of only three watts.

By suitably adjusting the resistance of the coil to the remainder of the circuit, including the path through the earth, by moving the switch f, I am enabled to secure currents sufficiently powerful to secure clear signals at varying distances. That is to say, by cutting out or cutting in more or less of the windings of the induction coil currents are readily produced proportional in strength to the distances they must traverse through the earth.

What I claim is:

1. The method of transmitting wireless intelligence which consists in joining the positive and negative poles of a source of low tension current, and the two ends of a self induction coil each to the earth through a plurality of pairs of earth contacts; in suitably adjusting the resistance of said coil to the rest of the circuit; and in suddenly reducing the low tension current flowing through said coil, ther eby, when said current is at its minimum impressing on said pairs of earth contacts a maximum voltage from the induced direct current through said coil; substantially as described.

2. The method of transmitting wireless signals which consists in suddenly reducin a low tension current passing through a selfinduction coil, thereby inducing in said coil a direct current of high electromotive force; in causing said induced current to be conducted to earth through a plurality of widely separated earth contacts; and in simultaneously preventing said low tension current from passing to the earth; substantially as described.

3. In an apparatus for sending wireless intelligence the combination of a source of low tension current; a self induction coil connected therewith; means to suddenly reduce the current passing through said coil and thereby produce a direct current of high tension in said coil when said first mentioned current is at its minimum; means to adjust the resistance and self inductance of said coil to correspond with other portions of the circuit; and a plurality of pairs of widely separated earth contacts joined to each other and to said coil; substantially as described.

4. In an apparatus for sending telegraphic and telephonic wireless signals, the combination of a source of low tension current; a self induction coil adapted to be placed in circuit therewith; a telephonic.

transmitter in circuit with said coil and said source; a telegraphic interrupter adapted to be placed in circuit with said source and said coil; a signal key adapted to suddenly break the circuit through said coil; and ground connections for each end of said coil; substantially as described.

5. In an apparatus for sending and receiving telephonic and telegraphic signals the combination of two ground connections, each consisting of a plurality of widely separated conductors joined together; a receiver normally in circuit with said connections; a battery; a self induction coil; a signal key adapted to break connection between said receiver and one of said ground connections, and to make circuit between said battery, said ground connection and one end of said coil; a microphone transmitter; a switch adapted to join the other end of said coil to said transmitter and to the other ground connection; a telegraphic in- ALEX. W. SHARMAN.

Witnesses:

HENRY BIRKBEOK, H. D. JAMEsoN. 

